Lateral distribution of N3 dye molecules on TiO2(1 1 0) surface

The lateral distribution of Ru(4,4′-dicarboxy-2,2′-bipyridine)2(NCS)2 (N3) dye molecules on a titanium dioxide (TiO2) surface was examined by using a scanning tunneling microscope. Pivalate ((CH3)3CCOO−) -covered rutile TiO2(1 1 0) surfaces were immersed in acetonitrile containing the N3 dye. The N3 molecules which replaced the pivalates were observed as protrusions embedded in the pivalate monolayer. A two-dimensional radial distribution function indicated that the adsorbed N3 molecules tended to be aggregated. Trapping of an N3 molecule in the solution by a preadsorbed N3 molecule was proposed as a driving force for the aggregation. The hydrogen bonds between the carboxyl groups of two N3 molecules contribute to the trapping.